Yep, you are right, I misread the column.
Yes, you can delete it.
Correct. Deleting a snapshot only deletes data exclusive to that snapshot. For example, let's say you have 100 files. You take a snapshot. The snapshot (a read only version of the filesystem) has 100 files in it. It takes up no space because those files are the same as the active dataset. Now you add a file. The current dataset now has 101 files. You delete the snapshot. You still have those 101 files.
Let's say you have 100 files. You take a snapshot. The snapshot has 100 files in it. (And again takes up no space.) Now you delete a file on the active dataset. You don't recover any space. Why? The snapshot still has that deleted file in it. So that space cannot be freed by the system. However, the current dataset only has 99 files now. So now you delete the snapshot. You still have those 99 files in the active dataset, but you free up the space from the file you deleted because the snapshot that contained that file has been deleted.
Make sense?